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Michael Lee Samsom, Heather Sheardown, Tannin A Schmidt; Proteoglycan 4 and Hyaluronan Lubrication Synergy at Silicone Hydrogel-Human Cornea Biointerfaces. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4655.
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Friction on the ocular surface may contribute to contact lens (CL) discomfort. Proteoglycan 4 (PRG4), a mucinous glycoprotein found in the eye, reduces friction between a cornea-eyelid interface. When PRG4 is combined with hyaluronan (HA), friction is reduced lower than with either alone, for a polydimethylsiloxane-cornea interface. This PRG4+HA synergy could be effective for silicone hydrogel (SH) CL materials. The aim of this study was to determine the lubricating ability of PRG4+HA, with HA in solution (HAsol) and incorporated into SH (HAinc), at a cornea-SH interface.
Fresh human corneas were obtained from the Alberta Lions Eye Bank. 2 model SH (pHEMA,Methacryloxypropyltris(trimethylsiloxy)silane [pHEMA TRIS] and N,N-Dimethylcrylamide, TRIS [DMAA TRIS]) lens materials were prepared. HA was also incorporated into DMAA TRIS [DMAA TRIS+HAinc]. PRG4 was obtained from bovine cartilage culture and suspended in saline at 300µg/mL. Tissues and CL materials were mounted on a BOSE ELF3200 biomechanical tester, forming a cornea-lens interface. These surfaces were articulated at effective sliding speeds of 0.3-30 mm/s, and pressures of 11-22 kPa. pHEMA TRIS and DMAA TRIS (n=4-5) were tested against corneas in saline, HAsol, PRG4 and PRG4+HAsol baths. DMAA TRIS+HAinc was compared to DMAA TRIS (n=4) in saline and PRG4. Static and kinetic friction coefficients were calculated.
HA+PRG4 synergism was observed for both HAsol and HAinc. Kinetic friction coefficients (mean over all speeds) for HEMA TRIS sequence (saline=0.31±0.03, PRG4=0.26±0.05, HAsol=0.23±0.04, PRG4+HAsol=0.17±0.04) showed lubricant effects for, HAsol and PRG4 as well as PRG4+HAsol synergism. DMAA TRIS (saline=0.15±0.02, PRG4=0.12±0.02, HAsol=0.16±0.02, PRG4+HAsol=0.10±0.02) showed lubricant effects for PRG4 and synergism for PRG4+HAsol, but no apparent effect of HAsol. The DMAA TRIS+HAinc (saline=0.14±0.01, PRG4=0.08±0.01) showed PRG4+HAinc synergism but no apparent effect of HAinc when compared to DMAA TRIS (saline=0.12±0.01, PRG4=0.10±0.01).
HA and PRG4 lubricated synergistically for model SH, and synergism was maintained with HA incorporated into the SH. HA alone only functioned as a lubricant in solution for pHEMA TRIS. Future studies will examine potential surface modification with HA and PRG4. This work could aid the development of novel CL materials with low friction and potentially better comfort.
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